This isn't just about industrial emissions, though certainly fossil fuel burning accounts for some outdoor air pollution. In fact, one of the main killers is pollution from indoor cooking fires, especially in regions of India and other parts of Asia where people cook over fires fueled with biomass. The smoke from these cooking fires can cause heart disease, strokes, and respiratory problems in children. Overwhelmingly, women are the ones who suffer as a result of this kind of air pollution, as they tend to be the ones cooking.

Outdoor air pollution causes slightly fewer deaths than indoor, but it remains a leading cause of death in the air pollution belt that runs from Japan and China, through India, and down to Southeast Asia. Many countries in this air pollution belt rely on coal or biomass as fuel, both of which produce a lot of toxic pollutants that lead to heart disease and cancer. But there are other causes of pollution too, such as slash-and-burn agricultural practices that left large parts of Sumatra on fire for most of the past month.

Peat fires in Sumatra have been burning for weeks, producing thick clouds of haze and smoke.…
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According to the WHO, these are the main causes of death from pollution:

Outdoor air pollution-caused deaths – breakdown by disease:

40% – ischaemic heart disease;

40% – stroke;

11% – chronic obstructive pulmonary disease (COPD);

6% - lung cancer; and

3% – acute lower respiratory infections in children.

Indoor air pollution-caused deaths – breakdown by disease:

34% - stroke;

26% - ischaemic heart disease;

22% - COPD;

12% - acute lower respiratory infections in children; and

6% - lung cancer.

The New York Times has a good report on the WHO's findings, noting that part of the problem comes from rapidly-industrializing areas. Countries like China and India are building instant cities that are low-density, and thus require more driving and energy use.